<?php
/**
* This class provides a simple interface for OpenID (1.1 and 2.0) authentication.
* Supports Yadis discovery.
* The authentication process is stateless/dumb.
*
* Usage:
* Sign-on with OpenID is a two step process:
* Step one is authentication with the provider:
* <code>
* $openid = new LightOpenID;
* $openid->identity = 'ID supplied by user';
* header('Location: ' . $openid->authUrl());
* </code>
* The provider then sends various parameters via GET, one of them is openid_mode.
* Step two is verification:
* <code>
* if ($this->data['openid_mode']) {
*     $openid = new LightOpenID;
*     echo $openid->validate() ? 'Logged in.' : 'Failed';
* }
* </code>
*
* Optionally, you can set $returnUrl and $realm (or $trustRoot, which is an alias).
* The default values for those are:
* $openid->realm     = (!empty($_SERVER['HTTPS']) ? 'https' : 'http') . '://' . $_SERVER['HTTP_HOST'];
* $openid->returnUrl = $openid->realm . $_SERVER['REQUEST_URI']; # without the query part, if present
* If you don't know their meaning, refer to any openid tutorial, or specification. Or just guess.
*
* AX and SREG extensions are supported.
* To use them, specify $openid->required and/or $openid->optional before calling $openid->authUrl().
* These are arrays, with values being AX schema paths (the 'path' part of the URL).
* For example:
*   $openid->required = array('namePerson/friendly', 'contact/email');
*   $openid->optional = array('namePerson/first');
* If the server supports only SREG or OpenID 1.1, these are automaticaly
* mapped to SREG names, so that user doesn't have to know anything about the server.
*
* To get the values, use $openid->getAttributes().
*
*
* The library requires PHP >= 5.1.2 with curl or http/https stream wrappers enabled..
* @author Mewp
* @copyright Copyright (c) 2010, Mewp
* @license http://www.opensource.org/licenses/mit-license.php MIT
*/
class LightOpenID
{
	public $returnUrl
		, $required = array()
		, $optional = array();
	private $identity, $claimed_id;
	protected $server, $version, $trustRoot, $aliases, $identifier_select = false
		, $ax = false, $sreg = false, $data;
	static protected $ax_to_sreg = array(
		'namePerson/friendly'     => 'nickname',
		'contact/email'           => 'email',
		'namePerson'              => 'fullname',
		'birthDate'               => 'dob',
		'person/gender'           => 'gender',
		'contact/postalCode/home' => 'postcode',
		'contact/country/home'    => 'country',
		'pref/language'           => 'language',
		'pref/timezone'           => 'timezone',
		);

	function __construct()
	{
		$this->trustRoot = (!empty($_SERVER['HTTPS']) ? 'https' : 'http') . '://' . $_SERVER['HTTP_HOST'];
		$uri = $_SERVER['REQUEST_URI'];
		$uri = strpos($uri, '?') ? substr($uri, 0, strpos($uri, '?')) : $uri;
		$this->returnUrl = $this->trustRoot . $uri;

		$this->data = $_POST + $_GET; # OPs may send data as POST or GET.
	}

	function __set($name, $value)
	{
		switch ($name) {
			case 'identity':
			if (strlen($value = trim((String) $value))) {
				if (preg_match('#^xri:/*#i', $value, $m)) {
					$value = substr($value, strlen($m[0]));
					} elseif (!preg_match('/^(?:[=@+\$!\(]|https?:)/i', $value)) {
						$value = "http://$value";
					}
					if (preg_match('#^https?://[^/]+$#i', $value, $m)) {
						$value .= '/';
					}
				}
				$this->$name = $this->claimed_id = $value;
				break;
				case 'trustRoot':
				case 'realm':
				$this->trustRoot = trim($value);
			}
		}

		function __get($name)
		{
			switch ($name) {
				case 'identity':
				# We return claimed_id instead of identity,
				# because the developer should see the claimed identifier,
				# i.e. what he set as identity, not the op-local identifier (which is what we verify)
				return $this->claimed_id;
				case 'trustRoot':
				case 'realm':
				return $this->trustRoot;
			}
		}

		/**
		* Checks if the server specified in the url exists.
		*
		* @param $url url to check
		* @return true, if the server exists; false otherwise
		*/
	function hostExists($url)
	{
		if (strpos($url, '/') === false) {
			$server = $url;
		} else {
			$server = @parse_url($url, PHP_URL_HOST);
		}

		if (!$server) {
			return false;
		}

		return !!gethostbynamel($server);
	}

	protected function request_curl($url, $method='GET', $params=array())
	{
		$params = http_build_query($params, '', '&');
		$curl = curl_init($url . ($method == 'GET' && $params ? '?' . $params : ''));
		curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
		curl_setopt($curl, CURLOPT_HEADER, false);
		curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
		curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
		curl_setopt($curl, CURLOPT_HTTPHEADER, array('Accept: application/xrds+xml, */*'));
		if ($method == 'POST') {
			curl_setopt($curl, CURLOPT_POST, true);
			curl_setopt($curl, CURLOPT_POSTFIELDS, $params);
			} elseif ($method == 'HEAD') {
				curl_setopt($curl, CURLOPT_HEADER, true);
				curl_setopt($curl, CURLOPT_NOBODY, true);
			} else {
				curl_setopt($curl, CURLOPT_HTTPGET, true);
			}
			$response = curl_exec($curl);

			if($method == 'HEAD') {
				$headers = array();
				foreach(explode("\n", $response) as $header) {
					$pos = strpos($header,':');
					$name = strtolower(trim(substr($header, 0, $pos)));
					$headers[$name] = trim(substr($header, $pos+1));
				}

				# Updating claimed_id in case of redirections.
				$effective_url = curl_getinfo($curl, CURLINFO_EFFECTIVE_URL);
				if($effective_url != $url) {
					$this->claimed_id = $effective_url;
				}

				return $headers;
			}

			if (curl_errno($curl)) {
				throw new ErrorException(curl_error($curl), curl_errno($curl));
			}

			return $response;
		}

		protected function request_streams($url, $method='GET', $params=array())
		{
			if(!$this->hostExists($url)) {
				throw new ErrorException('Invalid request.');
			}

			$params = http_build_query($params, '', '&');
			switch($method) {
				case 'GET':
				$opts = array(
				'http' => array(
					'method' => 'GET',
					'header' => 'Accept: application/xrds+xml, */*',
				'ignore_errors' => true,
					)
					);
				$url = $url . ($params ? '?' . $params : '');
				break;
				case 'POST':
				$opts = array(
				'http' => array(
					'method' => 'POST',
					'header'  => 'Content-type: application/x-www-form-urlencoded',
					'content' => $params,
					'ignore_errors' => true,
					)
					);
				break;
				case 'HEAD':
				# We want to send a HEAD request,
				# but since get_headers doesn't accept $context parameter,
				# we have to change the defaults.
				$default = stream_context_get_options(stream_context_get_default());
				stream_context_get_default(
				array('http' => array(
					'method' => 'HEAD',
					'header' => 'Accept: application/xrds+xml, */*',
				'ignore_errors' => true,
					))
					);

				$url = $url . ($params ? '?' . $params : '');
				$headers_tmp = get_headers ($url);
				if(!$headers_tmp) {
					return array();
				}

				# Parsing headers.
				$headers = array();
				foreach($headers_tmp as $header) {
					$pos = strpos($header,':');
					$name = strtolower(trim(substr($header, 0, $pos)));
					$headers[$name] = trim(substr($header, $pos+1));

					# Following possible redirections. The point is just to have
					# claimed_id change with them, because get_headers() will
					# follow redirections automatically.
					# We ignore redirections with relative paths.
					# If any known provider uses them, file a bug report.
					if($name == 'location') {
						if(strpos($headers[$name], 'http') === 0) {
							$this->claimed_id = $headers[$name];
							} elseif($headers[$name][0] == '/') {
								$parsed_url = parse_url($this->claimed_id);
								$this->claimed_id = $parsed_url['scheme'] . '://'
								. $parsed_url['host']
									. $headers[$name];
							}
						}
					}

					# And restore them.
					stream_context_get_default($default);
					return $headers;
				}
				$context = stream_context_create ($opts);

				return file_get_contents($url, false, $context);
			}

			protected function request($url, $method='GET', $params=array())
			{
				if(function_exists('curl_init') && !ini_get('safe_mode')) {
					return $this->request_curl($url, $method, $params);
				}
				return $this->request_streams($url, $method, $params);
			}

			protected function build_url($url, $parts)
			{
				if (isset($url['query'], $parts['query'])) {
					$parts['query'] = $url['query'] . '&' . $parts['query'];
				}

				$url = $parts + $url;
				$url = $url['scheme'] . '://'
				. (empty($url['username'])?''
					:(empty($url['password'])? "{$url['username']}@"
					:"{$url['username']}:{$url['password']}@"))
					. $url['host']
					. (empty($url['port'])?'':":{$url['port']}")
					. (empty($url['path'])?'':$url['path'])
					. (empty($url['query'])?'':"?{$url['query']}")
					. (empty($url['fragment'])?'':":{$url['fragment']}");
				return $url;
			}

			/**
			* Helper function used to scan for <meta>/<link> tags and extract information
			* from them
			*/
		protected function htmlTag($content, $tag, $attrName, $attrValue, $valueName)
		{
			preg_match_all("#<{$tag}[^>]*$attrName=['\"].*?$attrValue.*?['\"][^>]*$valueName=['\"](.+?)['\"][^>]*/?>#i", $content, $matches1);
			preg_match_all("#<{$tag}[^>]*$valueName=['\"](.+?)['\"][^>]*$attrName=['\"].*?$attrValue.*?['\"][^>]*/?>#i", $content, $matches2);

			$result = array_merge($matches1[1], $matches2[1]);
			return empty($result)?false:$result[0];
		}

		/**
		* Performs Yadis and HTML discovery. Normally not used.
		* @param $url Identity URL.
		* @return String OP Endpoint (i.e. OpenID provider address).
		* @throws ErrorException
		*/
	function discover($url)
	{
		if (!$url) throw new ErrorException('No identity supplied.');
		# Use xri.net proxy to resolve i-name identities
		if (!preg_match('#^https?:#', $url)) {
			$url = "https://xri.net/$url";
		}

		# We save the original url in case of Yadis discovery failure.
		# It can happen when we'll be lead to an XRDS document
		# which does not have any OpenID2 services.
		$originalUrl = $url;

		# A flag to disable yadis discovery in case of failure in headers.
		$yadis = true;

		# We'll jump a maximum of 5 times, to avoid endless redirections.
		for ($i = 0; $i < 5; $i ++) {
			if ($yadis) {
				$headers = $this->request($url, 'HEAD');

				$next = false;
				if (isset($headers['x-xrds-location'])) {
					$url = $this->build_url(parse_url($url), parse_url(trim($headers['x-xrds-location'])));
					$next = true;
				}

				if (isset($headers['content-type'])
					&& strpos($headers['content-type'], 'application/xrds+xml') !== false
				) {
					# Found an XRDS document, now let's find the server, and optionally delegate.
					$content = $this->request($url, 'GET');

					preg_match_all('#<Service.*?>(.*?)</Service>#s', $content, $m);
					foreach($m[1] as $content) {
						$content = ' ' . $content; # The space is added, so that strpos doesn't return 0.

						# OpenID 2
						$ns = preg_quote('http://specs.openid.net/auth/2.0/');
						if(preg_match('#<Type>\s*'.$ns.'(server|signon)\s*</Type>#s', $content, $type)) {
							if ($type[1] == 'server') $this->identifier_select = true;

							preg_match('#<URI.*?>(.*)</URI>#', $content, $server);
							preg_match('#<(Local|Canonical)ID>(.*)</\1ID>#', $content, $delegate);
							if (empty($server)) {
								return false;
							}
							# Does the server advertise support for either AX or SREG?
							$this->ax   = (bool) strpos($content, '<Type>http://openid.net/srv/ax/1.0</Type>');
							$this->sreg = strpos($content, '<Type>http://openid.net/sreg/1.0</Type>')
							|| strpos($content, '<Type>http://openid.net/extensions/sreg/1.1</Type>');

							$server = $server[1];
							if (isset($delegate[2])) $this->identity = trim($delegate[2]);
							$this->version = 2;

							$this->server = $server;
							return $server;
						}

						# OpenID 1.1
						$ns = preg_quote('http://openid.net/signon/1.1');
						if (preg_match('#<Type>\s*'.$ns.'\s*</Type>#s', $content)) {

							preg_match('#<URI.*?>(.*)</URI>#', $content, $server);
							preg_match('#<.*?Delegate>(.*)</.*?Delegate>#', $content, $delegate);
							if (empty($server)) {
								return false;
							}
							# AX can be used only with OpenID 2.0, so checking only SREG
							$this->sreg = strpos($content, '<Type>http://openid.net/sreg/1.0</Type>')
							|| strpos($content, '<Type>http://openid.net/extensions/sreg/1.1</Type>');

							$server = $server[1];
							if (isset($delegate[1])) $this->identity = $delegate[1];
							$this->version = 1;

							$this->server = $server;
							return $server;
						}
					}

					$next = true;
					$yadis = false;
					$url = $originalUrl;
					$content = null;
					break;
				}
				if ($next) continue;

				# There are no relevant information in headers, so we search the body.
				$content = $this->request($url, 'GET');
				if ($location = $this->htmlTag($content, 'meta', 'http-equiv', 'X-XRDS-Location', 'content')) {
					$url = $this->build_url(parse_url($url), parse_url($location));
					continue;
				}
			}

			if (!$content) $content = $this->request($url, 'GET');

			# At this point, the YADIS Discovery has failed, so we'll switch
			# to openid2 HTML discovery, then fallback to openid 1.1 discovery.
			$server   = $this->htmlTag($content, 'link', 'rel', 'openid2.provider', 'href');
			$delegate = $this->htmlTag($content, 'link', 'rel', 'openid2.local_id', 'href');
			$this->version = 2;

			if (!$server) {
				# The same with openid 1.1
				$server   = $this->htmlTag($content, 'link', 'rel', 'openid.server', 'href');
				$delegate = $this->htmlTag($content, 'link', 'rel', 'openid.delegate', 'href');
				$this->version = 1;
			}

			if ($server) {
				# We found an OpenID2 OP Endpoint
				if ($delegate) {
					# We have also found an OP-Local ID.
					$this->identity = $delegate;
				}
				$this->server = $server;
				return $server;
			}

			throw new ErrorException('No servers found!');
		}
		throw new ErrorException('Endless redirection!');
	}

	protected function sregParams()
	{
		$params = array();
		# We always use SREG 1.1, even if the server is advertising only support for 1.0.
		# That's because it's fully backwards compatibile with 1.0, and some providers
		# advertise 1.0 even if they accept only 1.1. One such provider is myopenid.com
		$params['openid.ns.sreg'] = 'http://openid.net/extensions/sreg/1.1';
		if ($this->required) {
			$params['openid.sreg.required'] = array();
			foreach ($this->required as $required) {
				if (!isset(self::$ax_to_sreg[$required])) continue;
				$params['openid.sreg.required'][] = self::$ax_to_sreg[$required];
			}
			$params['openid.sreg.required'] = implode(',', $params['openid.sreg.required']);
		}

		if ($this->optional) {
			$params['openid.sreg.optional'] = array();
			foreach ($this->optional as $optional) {
				if (!isset(self::$ax_to_sreg[$optional])) continue;
				$params['openid.sreg.optional'][] = self::$ax_to_sreg[$optional];
			}
			$params['openid.sreg.optional'] = implode(',', $params['openid.sreg.optional']);
		}
		return $params;
	}

	protected function axParams()
	{
		$params = array();
		if ($this->required || $this->optional) {
			$params['openid.ns.ax'] = 'http://openid.net/srv/ax/1.0';
			$params['openid.ax.mode'] = 'fetch_request';
			$this->aliases  = array();
			$counts   = array();
			$required = array();
			$optional = array();
			foreach (array('required','optional') as $type) {
				foreach ($this->$type as $alias => $field) {
					if (is_int($alias)) $alias = strtr($field, '/', '_');
					$this->aliases[$alias] = 'http://axschema.org/' . $field;
					if (empty($counts[$alias])) $counts[$alias] = 0;
					$counts[$alias] += 1;
					${$type}[] = $alias;
				}
			}
			foreach ($this->aliases as $alias => $ns) {
				$params['openid.ax.type.' . $alias] = $ns;
			}
			foreach ($counts as $alias => $count) {
				if ($count == 1) continue;
				$params['openid.ax.count.' . $alias] = $count;
			}

			# Don't send empty ax.requied and ax.if_available.
			# Google and possibly other providers refuse to support ax when one of these is empty.
			if($required) {
				$params['openid.ax.required'] = implode(',', $required);
			}
			if($optional) {
				$params['openid.ax.if_available'] = implode(',', $optional);
			}
		}
		return $params;
	}

	protected function authUrl_v1()
	{
		$returnUrl = $this->returnUrl;
		# If we have an openid.delegate that is different from our claimed id,
		# we need to somehow preserve the claimed id between requests.
		# The simplest way is to just send it along with the return_to url.
		if($this->identity != $this->claimed_id) {
			$returnUrl .= (strpos($returnUrl, '?') ? '&' : '?') . 'openid.claimed_id=' . $this->claimed_id;
		}

		$params = array(
			'openid.return_to'  => $returnUrl,
			'openid.mode'       => 'checkid_setup',
			'openid.identity'   => $this->identity,
			'openid.trust_root' => $this->trustRoot,
			) + $this->sregParams();

		return $this->build_url(parse_url($this->server)
			, array('query' => http_build_query($params, '', '&')));
	}

	protected function authUrl_v2($identifier_select)
	{
		$params = array(
			'openid.ns'          => 'http://specs.openid.net/auth/2.0',
		'openid.mode'        => 'checkid_setup',
			'openid.return_to'   => $this->returnUrl,
			'openid.realm'       => $this->trustRoot,
			);
		if ($this->ax) {
			$params += $this->axParams();
		}
		if ($this->sreg) {
			$params += $this->sregParams();
		}
		if (!$this->ax && !$this->sreg) {
			# If OP doesn't advertise either SREG, nor AX, let's send them both
			# in worst case we don't get anything in return.
			$params += $this->axParams() + $this->sregParams();
		}

		if ($identifier_select) {
			$params['openid.identity'] = $params['openid.claimed_id']
				= 'http://specs.openid.net/auth/2.0/identifier_select';
		} else {
			$params['openid.identity'] = $this->identity;
			$params['openid.claimed_id'] = $this->claimed_id;
		}

		return $this->build_url(parse_url($this->server)
			, array('query' => http_build_query($params, '', '&')));
	}

	/**
	* Returns authentication url. Usually, you want to redirect your user to it.
	* @return String The authentication url.
	* @param String $select_identifier Whether to request OP to select identity for an user in OpenID 2. Does not affect OpenID 1.
	* @throws ErrorException
	*/
function authUrl($identifier_select = null)
{
	if (!$this->server) $this->discover($this->identity);

	if ($this->version == 2) {
		if ($identifier_select === null) {
			return $this->authUrl_v2($this->identifier_select);
		}
		return $this->authUrl_v2($identifier_select);
	}
	return $this->authUrl_v1();
}

/**
* Performs OpenID verification with the OP.
* @return Bool Whether the verification was successful.
* @throws ErrorException
*/
function validate()
{
	$this->claimed_id = isset($this->data['openid_claimed_id'])?$this->data['openid_claimed_id']:$this->data['openid_identity'];
	$params = array(
		'openid.assoc_handle' => $this->data['openid_assoc_handle'],
		'openid.signed'       => $this->data['openid_signed'],
		'openid.sig'          => $this->data['openid_sig'],
		);

	if (isset($this->data['openid_ns'])) {
		# We're dealing with an OpenID 2.0 server, so let's set an ns
		# Even though we should know location of the endpoint,
		# we still need to verify it by discovery, so $server is not set here
		$params['openid.ns'] = 'http://specs.openid.net/auth/2.0';
		} elseif(isset($this->data['openid_claimed_id'])) {
			# If it's an OpenID 1 provider, and we've got claimed_id,
			# we have to append it to the returnUrl, like authUrl_v1 does.
			$this->returnUrl .= (strpos($this->returnUrl, '?') ? '&' : '?')
				.  'openid.claimed_id=' . $this->claimed_id;
		}

		if ($this->data['openid_return_to'] != $this->returnUrl) {
			# The return_to url must match the url of current request.
			# I'm assuing that noone will set the returnUrl to something that doesn't make sense.
			return false;
		}

		$server = $this->discover($this->data['openid_identity']);

		foreach (explode(',', $this->data['openid_signed']) as $item) {
			# Checking whether magic_quotes_gpc is turned on, because
			# the function may fail if it is. For example, when fetching
			# AX namePerson, it might containg an apostrophe, which will be escaped.
			# In such case, validation would fail, since we'd send different data than OP
			# wants to verify. stripslashes() should solve that problem, but we can't
			# use it when magic_quotes is off.
			$value = $this->data['openid_' . str_replace('.','_',$item)];
			$params['openid.' . $item] = get_magic_quotes_gpc() ? stripslashes($value) : $value;

		}

		$params['openid.mode'] = 'check_authentication';

		$response = $this->request($server, 'POST', $params);

		return preg_match('/is_valid\s*:\s*true/i', $response);
	}

	protected function getAxAttributes()
	{
		$alias = null;
		if (isset($this->data['openid_ns_ax'])
			&& $this->data['openid_ns_ax'] != 'http://openid.net/srv/ax/1.0'
		) { # It's the most likely case, so we'll check it before
		$alias = 'ax';
	} else {
		# 'ax' prefix is either undefined, or points to another extension,
		# so we search for another prefix
		foreach ($this->data as $key => $val) {
			if (substr($key, 0, strlen('openid_ns_')) == 'openid_ns_'
				&& $val == 'http://openid.net/srv/ax/1.0'
			) {
				$alias = substr($key, strlen('openid_ns_'));
				break;
			}
		}
	}
	if (!$alias) {
		# An alias for AX schema has not been found,
		# so there is no AX data in the OP's response
		return array();
	}

	$attributes = array();
	foreach ($this->data as $key => $value) {
		$keyMatch = 'openid_' . $alias . '_value_';
		if (substr($key, 0, strlen($keyMatch)) != $keyMatch) {
			continue;
		}
		$key = substr($key, strlen($keyMatch));
		if (!isset($this->data['openid_' . $alias . '_type_' . $key])) {
			# OP is breaking the spec by returning a field without
			# associated ns. This shouldn't happen, but it's better
			# to check, than cause an E_NOTICE.
			continue;
		}
		$key = substr($this->data['openid_' . $alias . '_type_' . $key],
			strlen('http://axschema.org/'));
		$attributes[$key] = $value;
	}
	return $attributes;
}

protected function getSregAttributes()
{
	$attributes = array();
	$sreg_to_ax = array_flip(self::$ax_to_sreg);
	foreach ($this->data as $key => $value) {
		$keyMatch = 'openid_sreg_';
		if (substr($key, 0, strlen($keyMatch)) != $keyMatch) {
			continue;
		}
		$key = substr($key, strlen($keyMatch));
		if (!isset($sreg_to_ax[$key])) {
			# The field name isn't part of the SREG spec, so we ignore it.
			continue;
		}
		$attributes[$sreg_to_ax[$key]] = $value;
	}
	return $attributes;
}

/**
* Gets AX/SREG attributes provided by OP. should be used only after successful validaton.
* Note that it does not guarantee that any of the required/optional parameters will be present,
* or that there will be no other attributes besides those specified.
* In other words. OP may provide whatever information it wants to.
*     * SREG names will be mapped to AX names.
*     * @return Array Array of attributes with keys being the AX schema names, e.g. 'contact/email'
* @see http://www.axschema.org/types/
*/
function getAttributes()
{
	if (isset($this->data['openid_ns'])
		&& $this->data['openid_ns'] == 'http://specs.openid.net/auth/2.0'
	) { # OpenID 2.0
		# We search for both AX and SREG attributes, with AX taking precedence.
		return $this->getAxAttributes() + $this->getSregAttributes();
	}
	return $this->getSregAttributes();
}
}
